This stampless folded letter originated in
Angouléme
about 100 km north northeast of Bordeaux in west central France.
(Angouléme
is the site of an annual carton festival and a cartoon museum.)It received a nice CDS and was marked with a boxed
PD for Paye á Destination
(Paid to Destination) indicating the letter fees had been prepaid.
The rate calculation was also included: 14 + 19 = 33.

A Paris receiving mark was applied on the
letter's arrival on April 27.
There is a partial London Foreign Branch receivingmark at the bottom.*
The Foreign Branch dealt with all foreign mail including delivery in
Central London.
The Foreign Branch also applied the curved FOREIGN PAID banner. It was also rerated for the
English portion of the
journey
and marked with an additional boxed PD.
I believe the /9 is indicative of the English rate of 9 pence.

Mail to be delivered outside of Central
London was
transferred to the General Post Office or the London Local Post.
On the arrival of this letter at the GPO on
April 29
it was marked
with the PAID tombstone applied to all incoming prepaid mail from all
sources.

The L|AP 29|M in the lozenge (diamond with
truncated points) is a receiver mark for Liverpool.

The addressee was Thomas
Leathers Equine, Merchant.

*Many thanks to Orthorpteran for his help
in understanding operations of the London post offices in 1839!
I hope I've interpreted his comments properly.